[UI] Minor - Bad order when sorting by "Active" in the Masternodes tab

[sabhiram]

If you sort the MNs by "Active" time, it will place 9d as older than 99d. This should be super easy to fix :)

[Fuzzbawls]

https://github.com/PIVX-Project/PIVX/blob/master/src/qt/masternodelist.cpp#L2

Current coding standards doc: https://github.com/PIVX-Project/PIVX/blob/master/doc/coding.md (this will be changing to a different filename shortly)

[sabhiram]

The simple way to fix this would be to fix DurationToDHMS to pad days like we do hours, but thats icky.

The right way to fix this is to probably subclass QTableWidgetItem to something like DHMSTableWidgetItem which is constructed using the duration in seconds and automagically uses that private member to do the comparison while displaying some nicely human friendli-ized text.

If this is not fixed in the next few days, and I find myself wanting to compile my wallet - ill take a stab at this :)